Hypoxia in Pilots at Higher Altitudes

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Table of Contents

Introduction
Literature Review
Methodology
Analysis/Discussion
Conclusion
Recommendations
Reference List
Footnotes

Introduction

The paper presents a review, analysis and a study on hypoxia faced by pilots at higher altitudes. The problems faced by pilots of commercial flights and the ways and means of dealing with them with the use of technology used in military planes will be the point of discussion and focus.

The usage of technology that minimize the conditions of hypoxia at higher altitudes and reduction of its negative effects on pilots who deal with the decision-making process while flying will be analyzed, and recommendations will be given.

Literature Review

Hypoxia and Flying

One of the foremost things of the primary requirements of humans is air. The lack of air, most specifically oxygen leads to hypoxia. Initially, hypoxia has been reported at high altitudes on mountains by mountaineers and after the invention of aero planes, the pilots and flight attendants are experiencing the effects of hypoxia and are feeling stressed.

This can be termed as ‘decompression sickness’ (Aronson K.S; 1991, 26) and has been first recognized or occurred in 1841. According to Aronson K.S (1991, 26) French mining engineer M. Triger ‘noticed symptoms experienced by miners after working in deep mine shafts’ (Aronson K.S; 1991, 26). Number of workers had been prone to joint pains and became vulnerable to paralysis.

However, the same sickness can be felt in a reverse manner, which can be known as hypoxia, when pilots fly in the air in a plane. While they fly in the air, they experience decompressed air and don’t have enough oxygen in the air, they breathe that is required for normal metabolic activities of the body.

Though the effects of hypoxia are not the same in different pilots, but it cannot be ignored as the effects are noticeable. In this regard, Aronson K.S (1991, 26-27) mentions about Paul Bert who is famous with the name ‘father of altitude physiology’.

As per the information provided about Paul Bert’s observations, though the commercial flights flying at a height of around 20,000 feet, with the pressurized atmosphere, still there is a lack of pressure of oxygen as the pressurization is only enough if the aircraft flies at 8,000 feet. That means the commercial aircrafts are flying at a height of around 20,000 feet with the pressurized atmosphere that suits the altitude of 8,000 feet, which results in hypoxia in pilots and flight attendants.

Aronson K.S (1991, 28) explains that when one goes to 18,000 feet above the sea level, the atmospheric pressure will be reduced to half of the standard pressure of one atmosphere.

That means the oxygen availability also decreases by half of the amount that is available at the normal atmospheric pressure at sea level. Consequently, the pilots and flight attendants who face this situation almost daily suffer from hypoxia (Aronson K.S: 1991, 25-28).¹

Thus, pilots and flight attendants are mostly associated with hypoxia. Though the commercial air craft cabins do have enough induced pressure for the safety and health of passengers and crew, the hypoxia depends on altitude.

According to Sharma L (2007), at an altitude of 8,000 feet, people in flight may experience mild hypoxia (Sharma L; 2007), even in the presence of the pressurized atmosphere. That means the pressurized atmosphere is lacking oxygen, and it is necessary to pressurize the flight interiors with oxygen.

Exposure to hypoxia can be considered into two categories. Simply being exposed to hypoxia and working in the atmosphere of hypoxia. Pilots and flight attendants do work in the hypoxia atmosphere, and it may result in headache and loss of memory, which may affect future working status of pilots.

The hypoxia may lead to stress, headache, backache, disturbed sleep, hearing problems and so on. Hence, ‘the nature and extent of physical/physiological problems and discomforts experienced by pilots’ (Sharma L; 2007) need to be examined, and a study is necessary to decide on the cause for the problems and difference from the normal state they are facing while in and after the flying hours.

It is necessary to know about the variation of effects of hypoxia if any on the persons depending on their age and sex. As the effects of hypoxia may or may not present for a long-time, it is necessary to conduct tests on the pilots regarding hypoxia for each flight or in some airlines, they test pilots for the effects of hypoxia before each flight (Sharma L: 2007)² so that necessary medication could be given.

However, according to Good W.A (1991, 104) the performance of the pilots might be degraded with ‘both prescribed and over the counter medications as well as by the medical conditions for which they are taken’ (Good W.A; 1991, 104).

Normally, the medicines of hypoxia are sedative, tranquilizer or antihistamine. These medicines make a pilot ‘much more susceptible to hypoxia’ (Good W.A; 1991, 104) and hence it is necessary for the pilots to minimize the use of over the counter medicines.

In addition to the above precautions alcohol can impair the pilot even many hours after its consumption and digestion due to hangover. The impairment of pilot may cause flight accidents and some of the major accidents give ground to the argument that hypoxia may be the reason for the inability that caused the accident.

For example, two accidents at Dallas and Fort Worth involving Delta Airlines alongside the accident in Denver by the flight of continental airlines proved that the pilots are the cause for the fatal happening, and hypoxia may be the reason for it.

Another accident in Washington DC due to Air Florida flight, alongside the crash of North West flight in Detroit could be some more examples, where pilots are blamed for the happenings, and hypoxia may be a cause for it. Hence, one cannot rule out the role of hypoxia in flight crashes as it impairs the pilots’ ability to deal with the situation (Good W.A: 1991, 104-105).³

Pressurized Atmosphere and Hypoxia

As hypoxia affects the ability of the pilot to deal with the adverse situations, modern aircraft are capable of operating at very high altitudes. The capability is due to the attempt to prevent hypoxia with the pressurized atmosphere. However, due to any unforeseen circumstances as if ‘sudden loss of cockpit pressure presents a life threatening hypoxia situation, requires an immediate response’ (Lindeis A.E, Fraser W.D & Fowler B; 1997).

To deal with the above-mentioned situations of rapid decompression situations that lead to hypoxia, the modern military aircrafts are having a system that gets the plane down to deal with the decompression and can be provided for commercial aircrafts also in the future.

The rapid get down of the plan in the condition of decompression is to minimize the effect of or slow down the onset of hypoxia by descending to a safe altitude, where the decompression at higher altitude could be controlled. To do this with commercial aircrafts also, a series of experiments had been done to reduce the impairment of pilot performance due to rapid de-compression.

However, there exists severe hurdle to these experiments as to measure the performance of a pilot in these circumstances is very difficult as it depends on physiological state of the pilot. To minimize the physiological problems of pilots, the system has two features. One is related to breathing and another to put enough pressure on the body.

The breathing system is known as positive-pressure breathing (PPB) through a mask. The second feature that consists of a jerkin with inflatable bladders puts pressure on limbs, chest, lungs and abdomen thus minimizing the effect of decompression or hypoxia. The PPB is to delay the collapse of blood circulation system and hypoxia as well.

The main hurdle to extend the usage of this system to commercial flights also is because it is necessary to provide these suits and masks to all the passengers, which is commercially not viable.

However, the present review is regarding the effect of hypoxia on pilots, its consequences and ways and means of minimizing or avoiding it, the ‘first aim of the experiments was to determine the degree of performance impairment under rapid decompression and the extent the PPB can help in reducing it.

The hypoxia may result in affecting the ‘visual serial choice reaction time (SCRT) task of the pilots, which may prove fatal and thus immediate reduction of hypoxia is necessary to avoid accidents in commercial planes. In addition to that Lindeis A.E, Fraser W.D & Fowler B (1997) explains that the possible causes of performance deficit indicate hypoxia as it decreases the arterial blood oxygen saturation.

This decrease in saturation may result in slowing of reaction time for pilots and may result in accidents. Hence, hypoxia and its effects are to be studied to provide more comfortable and safety measures for pilots to reduce the contexts of performance deficits while flying (Lindeis A.E, Fraser W.D & Fowler B: 1997).⁴

Conclusion: The literature review concludes that the hypoxia results in impairment of the pilot and may affect his/her decision making capability. Hence, it is necessary to contemplate about the safety measures that avoid the effects of hypoxia on pilots and minimize the negative effects on decision making capability.

Methodology

The methodology involved in this paper is a qualitative analysis of the topic with the help of available literature. The analysis has been supported by literature review, which provided enough background for the aspects that should be considered during analysis.

The review starts from finding of effects of hypoxia to the effects of it on pilots and flight attendants and the measures that need to be taken to minimize or reduce it.

The technology that helps in minimizing the effect of hypoxia and the possibility of usage of it has been reviewed, and the analysis will take place according to the aspects and conclusion of the review and as per the necessities of pilots, which help in reducing flight mishaps and improve air safety.

Analysis/Discussion

As far as the effects of hypoxia are considered, the ‘provision of the pilot against high sustained accelerations, against hypoxia’ (AEAT; 1993, 2) needs to be considered. The decompression effects at high altitude could be minimized by the technology that provides breathing gas.

The breathing air can be provided from ‘engine bleed air’. To do this, ‘molecular sieve oxygen generator, which works on pressure breathing on exposure to acceleration( (AEAT; 1993, 2) is necessary as it provides not only oxygen necessary to breathe comfortably but also the minimum pressure necessary for the body to be normal at high altitudes, which result in decompression.

That means to avoid the state of decompression and lung collapse; there should be a system in the cabin that provides pressure and oxygen respectively. To do so, protective garments are necessary as the mask provides oxygen for lungs and garment exerts enough pressure on the body in a decompressed atmosphere.

In addition to that it is necessary to provide inward relief to the pilots as they experience suffocation due to lack of supply of oxygen. The cabin and other places in an aircraft need to have systems to replenish the back-up oxygen in case of decompression emergencies as the pilots may not take the right decision while they suffocate.

The commercial plane makers can take a cue from the systems in war planes that provide ‘higher degree of protection and mobility’ (AEAT; 1993, 3) for the pilots. In this regard AEAT (1993, 3) explains about liquid conditioning to full coverage anti g trousers, necessary for the pilots to face decompressed and hypoxia situations.

However, the system and the garments provided to the pilots should be selected and made after taking into consideration functional characteristics. They are ‘operational life support, operational escape and survival, and personal’ (AEAT; 1993, 3).

The operational life support should enable the pilot to take decisions regarding flight safety, which means the safety of passengers alongside self. The operational escape survival should consider the aspects that help the flight crew and passengers to escape in case of emergency.

However, in commercial flights, operational life support is necessary as it is difficult to train the passengers regarding escape and survival attempts. However, operational life support equipment could be provided so that it could help the passengers also in the case of emergency.

However, as the paper is about hypoxia and its effects on pilots and their decision making, the operational life support for the pilots is of utmost importance. The oxygen masks and pressure breathing garments can provide with the necessary operational life support necessary in the case of decompression and hypoxia faced by the pilots (AEAT: 1993, 1-3).⁵

This is due to the fact that at high altitudes, ‘the human body experiences hypoxia when it tries to adapt to lower atmospheric pressure and reduced oxygen level as well’ (Penetar D.M, Friedl K.E; 2004, 272). This results in increased heart rate, cardiac output and respiration rate as it is necessary to ensure sufficient supply of oxygen to the body parts.

To ensure that supply the above-mentioned activities will increase, and they return to the normal when the atmospheric pressure returns to normal.

The changes in respiration, heart output and blood circulation result in change in the mood and it affects the physical and mental performance of the pilots. Hence, the safety measures and systems that are to be included in the flights should work in a manner to normalize the above mentioned increased activities.

The increased heart output and blood pressure also results in a decrease of endurance of the body, and the consequence is the need of exercise performance. The decrease of endurance decreases the situation that allows to work and yet times may demand the days and weeks of exposure to enough oxygen.

Hence, after every flight, it is necessary to examine the pilots for the status of endurance, physical fitness and mental stability as well. If this can be seen as an exaggerated response, they should be checked for the above features once in a stipulated period of time.

This is because, Penetar D.M, Friedl K.E (2005, 273) explains that psychomotor performance would be degraded with the ascent of altitudes above 4,300 meters, and the accuracy of the decision-making process would be impaired.

Penetar D.M et al (2005) further continues that there would be a delay in reaction and significant impairment of cognitive performance, which is necessary for the pilots while taking decisions during flight.

One measure that can be taken to reduce hypoxia though not up to the desired extent is not to ascend rapidly to altitudes above 1,800 meters (6000 feet) as that may put the individuals at risk and if the pilots are put at risk whole flight will be at risk.

Hence, the intensity of effect of hypoxia depends on rapidness in the initial ascent, and if it could be reduced the intensity of the effect of hypoxia also could be reduced. As a result, alongside the systems that deal with decompression and lack of oxygen, the rules and regulations should stipulate the slow ascent to delay and minimize the effects of decompression and hypoxia.

Penetar D.M, Friedl K.E (2005, 274) further explains that aviation equipment needs to be designed to provide enough haemoglobin saturation to pilots. This could be helpful in hypoxic environment and these systems are widely used only in military planes, but not in commercial flights.

Hence, these systems need to be modified according to the usage of commercial flights and offered to the pilots so that they could deal with hypoxic conditions successfully and this also helps them to remain fit even after continuous and frequent exposure to hypoxic conditions.

The systems that deal with decompression sickness also should be considered as ‘Air Force over the past 20 years, with thousands of simulated altitude exposures revealed a 41 percent incidence of decompression symptoms’ (Penetar D.M, Friedl K.E: 2005, 272-275).⁶

Conclusion

The hypoxia is the worst situation that any pilot can face while flying and can be considered as a major concern in aviation industry. As the safety of the passengers depends on the decision making capability and physiological condition of the pilot and flight attendants, it is necessary to have systems that deal with hypoxia and decompressed atmosphere.

The systems should provide operational life support to enable the pilot to perform the duties in conditions of decompression and hypoxia. The review and analysis concluded on the facts of development of systems that provide oxygen and pressure as well in the high altitudes for pilots.

Recommendations

It is necessary to provide oxygen and pressure in the cabin of the pilots to increase their decreased endurance due to decompression and hypoxia.
To deal with hypoxia, the systems should provide oxygen for breathing.
To deal with the decompressed atmosphere, the systems should provide pressure in the cabin so that the pilots can work in normal atmospheric pressure conditions.
It is necessary to examine the pilots for their physiological conditions once in a stipulated period to find the negative effects of hypoxia on them if any.
There should be institutional arrangements in aviation industry to deal with the decreased physical endurance of pilots.

Reference List

AEAT. (1993). SAFE Europe Symposium 1993. Aircraft Engineering and Aerospace Technology. 66 (1). Pp.2-4.

Aronson K.S. (1991). Flight: The Physiological Stresses. In Sheila R. Deitz and William E. Thoms, eds., Pilots, Personality, and Performance: Human Behavior and Stress in the Skies. New York: Quorum Books. Pp. 25-28.

Good W.A. (1991). The Post-Deregulation Pilot Job Market: Pilot Error or Personnel Economics?. In Sheila R. Deitz and William E. Thoms, eds., Pilots, Personality, and Performance: Human Behaviour and Stress in the Skies. New York: Quorum Books. Pp.104-105.

Lindeis A.E, Fraser W.D & Fowler B. (1997). Performance during Positive Pressure Breathing after rapid decompression up to 72000 feet. Human Factors. 39(1).

Penetar D.M, Friedl K.E. (2004). The Physiology of Performance, Stress and Readiness, in James W. Ness, Victoria Tepe, and Darren R. Ritzer (ed.) The Science and Simulation of Human Performance: Advances in Human Performance and Cognitive Engineering Research. Volume 5. Emerald Group Publishing Limited. pp.267-305

Sharma L. (2007). Lifestyles, Flying and Associated Health Problems in Flight Attendants. Perspectives in Public Health. 127(6).

Footnotes

¹ Aronson K.S. (1991). Flight: The Physiological Stresses. In Sheila R. Deitz and William E. Thoms, eds., Pilots, Personality, and Performance: Human Behavior and Stress in the Skies. New York: Quorum Books. P. 25-28.

² Sharma L. (2007). Lifestyles, Flying and Associated Health Problems in Flight Attendants. Perspectives in Public Health. 127(6).

³ Good W.A. (1991). The Post-Deregulation Pilot Job Market: Pilot Error or Personnel Economics?. In Sheila R. Deitz and William E. Thoms, eds., Pilots, Personality, and Performance: Human Behaviour and Stress in the Skies. New York: Quorum Books. P.104-105.

⁴ Lindeis A.E, Fraser W.D & Fowler B. (1997). Performance during Positive Pressure Breathing after rapid decompression up to 72000 feet. Human Factors. 39(1).

⁵ AEAT. (1993). SAFE Europe Symposium 1993. Aircraft Engineering and Aerospace Technology. 66(1). Pp.2-4.

⁶ Penetar D.M, Friedl K.E. (2004). The Physiology of Performance, Stress and Readiness, in James W. Ness, Victoria Tepe, and Darren R. Ritzer (ed.) The Science and Simulation of Human Performance (Advances in Human Performance and Cognitive Engineering Research, Volume 5). Emerald Group Publishing Limited, pp.267-305

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